The long-term goals of this project are several: Aim 1) By studying patients, to develop better methods for diagnosis and therapy of paraneoplastic syndromes affecting the nervous system, to identify previously unreported paraneoplastic syndromes, and to better understand the pathogenesis of autoantibody-associated paraneoplastic syndromes and their effect on the growth and development of the accompanying cancer. To carry out this aim, sera and cerebrospinal fluid (CSF) from patients with suspected paraneoplastic syndromes will be studied by immunohistochemistry and Western blotting of both nervous system and tumor tissue to identify new autoantibodies that react with both nervous system and tumor tissue (i.e. antibodies that identify "onconeural" antigens). In available patients, whole blood will be procured for HLA typing, for development of human monoclonal antibodies and for identification of specific activated T cells. A computerized database, collected under the auspices of this grant over the past 7 years and containing more than 2500 patient records, will be searched for previously uncharacterized autoantibodies and these, along with any newly discovered autoantibodies, will be further characterized and their genes cloned. A therapeutic protocol that suppresses CNS and peripheral immune cells by radiation therapy delivered to both lymph nodes and CNS will be utilized in a pilot study. The effects of radiation on the neurological disorder as well as on serum and CSF autoantibodies and inflammatory infiltrates will be measured. Aim 2) In experimental animals, to develop a model of several of the paraneoplastic syndromes in order to dissect the pathogenesis of the immune response. Plans to develop an animal model include introduction of paraneoplastic genes into established mouse tumor lines followed by their implantation into mice, injection of scid mice with immune cells from newly diagnosed patients with autoantibody-positive paraneoplastic syndromes, immunization of pregnant mice to determine the effect of autoantibodies on the fetus, injection of antigen presenting cells expressing paraneoplastic antigens into syngeneic mice, and inhibition of expression of paraneoplastic genes in neural cells of animals using antisense oligonucleotides and viral vectors carrying paraneoplastic genes in the antisense direction. Aim 3) In vitro, to study cytotoxicity of antibodies in tumors by exposing cultured tumor and neuronal cell lines expressing paraneoplastic antigens in the presence and absence of complement, and to determine the effect of inhibition of expression of paraneoplastic proteins in tumor and neuronal cell lines using antisense oligonucleotides and defective viral vectors carrying the paraneoplastic genes in antisense direction.